Loom dobby



V. LINDSJO April l2, 19532.

LOOM DOBBY Filed Feb. 5, 1951 2 Sheets-Sheet l \nve.nTor.

Verner L ndsJ' o ita'ntfof fa crank motion.

this is not true of the position. This because in the crank motion the crank pin moves through an arc of less than 90o from its top position to bring the upper end of the link 23 or the point 28 to its mid position of traveland through an arc of more than 90O to carry this point 28 to the lower end of its travel. This is simply a con'coIn- This means that the dobby knives will not be in position to cause the jacks to be at their mid positions when the crank is at a position half-way loetween its uppermost-.and lowermost positions. Consequently lthe shed will not be quite closed when the lay beats up andthe harness frames will, moreover, be in opposite positions for this slightly open shed at alternate beat-ups of the lay. This tends to produce 'unevenness in the weaving operation. 2o.

In. the present invention the desirable crank motion for operating the dobby mechanism is retained butthe construction is so altered as tocause the dobby knives to bring thejacks to theirmid positions each time the crank pin is midway of its path oftravel from its uppermost to its lowermost position. This brings the dobby mechanism in time with the period of the lay operation and 30.: secures the closing of the shed at the same point ateach beat-up of the lay or the same period in the cycle of the loom operation.

Two similar means for securing this result are illustrated` diagrammatically in Figs. 2 and 3 of the drawings.

InFig. 2the elements of the mechanism are represented simply by lines and the various pivotal connections by points. ASince it makes little difference whether the crank arm 19 is rotating in a plane transversely to the rocker arm 6 or in the plane thereof, it is shown for convenience in the latter position and the same is true of the crank shaft of the loom. trateddiagrammatically the crank shaft 2, the crank l29 for operating the lay, vthe cam shaft 3, crank arm 19, the crank pin 20, the link 23,'. the three-armed lever comprising the central arm 8 pivotedl at 28 to the link 23, the upper arm 9 and the lower arm 10 with this three-armed lever pivoted at 7, the dobby knives 12 connected by the link 11 at 30 to,

the arm 9 and 15 Aconnected by the link 14 at V31 to the arm 10.

In the present invention the angular'relation of the'knife-operating arms 9 and 10 with respect to the center arm 8 of the three# armed lever, the angular relation of the paths 13 and 16of the knives which, it will'bc noted, is symmetrical with respect tothe horizontal, the lengthof the paths of Vtravel 13 and 16 of the knives required to move the jacks from oneend position-to the other, andl the length of the knifeoperatingarms 9 and 10, are correlated so that when the crank pin 2() is at either of its positions d midway of I have, then, in Fig. 2 illus-vv its arc of travel between its extreme jack moving positions a and c, the knives 12 and 15 will be in suc-h a position in their paths of travel 13 and 16 as to bring the jacks to their mid positions. This means that the arm 8 andthe pivotal point 28 will be determined by moving the three-armed lever until the crank pin 2G is at the point lZ) or d. The extreme positions shown in dotted lines 8a, Scare de termined by themovement of the crank pin 20 to the points a,c. Hence it is only necessary so to construct the three-armed lever that the, arm 9 and link 11 shall move the dobby knife 12 'to' the end positions required to bring the jacks to their end positions coincidentally with the movement of the arm 8 to the extreme limits of its travel and that the dobby knife 12 shall reach such a point in its path of travel as to bring the jacks to mid position when the armf8 is in the position illustrated, that is, with thecrank 20 at Z) or cl. The same thing must'be true of the arm 10 and the dobby knife` 15. The simplest way to effect this construction is .to lay it out graphically by the cut and try method. The angle between the positions 8a, and 8c being fixed and the mid position of the jacks being fixed, it is only necessary to select lengths of arms 9 and 1() which, when swung through an angle equal to the angle between 8a, and 80, shall give the desired result. The shifting of these arms 9'and 10 into the requiredpositions enables unequal angular movements thereof to Vgive equal movements of travel of the dobby knives because unequal movements of the points and 31 in theirv arcs of travel may be resolved into equal movements in the travel of the point 12 in the straight line path 13 and the point 15 in its fstraight line path` Vthe knives will be oppositelyrdisposed with the jacks at their end positions. Y y y A. similar construction is shown in Fig. 3 and is obtained in a similar manner, the only ditference'being that in this case the arm 8 of the three-armedleveris shown in a horizontal position when the `jacks are at theirmid position. To secure this construction the link 23 is lengthenedout slightly so that when the crank pin 20 is in positional), the pivotal point 28 is on a horizontal line extending through the pivot 7. Y The construction of the `three-armed levenmay then be arrivedat graphically in the manner already described.

It will thus be seen that a three-armed lever may bereadily constructed which withoutV other change in the construction or the dobby will enable the dobby mechanism to operate with perfect accuracy'while still employing thecrank motion so as to cause the'shed to close in the same period in the cycle of the loom each time. For example, in Figs. 2 and 3 it is assumed that the lay is at back center at the point a, c and at front center at the point b, d and since the crank shaft 2 is revolving once to each two rotations of the cam shaft 3, it follows that the jacks will beat their mid positions each time the lay reaches front center and consequently the shed will be closed at the same period in the cycle of the loom at all times.

Having thus described the invention, what is claimed as new, and desired to be secured by Letters Patent, is:

l. A loom dobby comprising a pair of sliding harness frame jack-operating knives, a three-armed lever fulcrumed midway the planes of movement of the knives to swing in a plane transversely of the knives, a crank, a link connecting the crank and the center arm of the lever, and links connecting the other ,arms of the lever respectively to the knives,

in which the angular relation of the knifeoperating arms to the' center arm of the lever,

the angular relation of the paths of the knives, the length of travel of the knives required to operate the jacks and the length of.

the knife-operating arms are'correlated to cause the knives to bring the jacks to their mid positions when the crank is at either mid point or' its arc of movement between its eXtremejack moving positions. f Y

` 2. A loom dobby comprising a pair of sliding harness frame jack operating knives, a three-armed lever fulcrumed midway the planes of movement of the'knives to swing in a plane transverselyof the knives, a crank, a

` link connecting the crank and thecenter arm ofthe lever, and links connecting the other arms of the lever respectively tothe knives, in which the `angularrelation of the knifeoperating arms to the center arm of the lever, the angular relation of the paths of the knives, the length of the travel of the knives requiredto operate t-he jacks and the length of the knife-operating arms are correlated to cause the knives to bring the -jacks to their mid positions when the crank is at either mid point of its are of movement between its extreme jack-moving positions and to cause the knives to be oppositely disposed-.with the jacks at their end positions when the crank is at either of its eXtreme tions. Y

3. In a loom, a dobby having a pair of sliding harness frame jack opera-ting knives, a three-armed lever fulcrumed midway the planes of movementofthe knives to swing in a plane transversely of the knives, a crank, a link connecting the crank and the center arm of the lever, links connecting the other arms of the lever respectively to the knives, and a lay operating crank shaft rotating once to each two rotations of the dobby crank in which vthe angular relation of the `knifejack-moving posipoint'of its arc of movement between opelratingiarmste'thecenter,arm.otliefleveig` the: angular relation; iofthe? pat-hs ot `tltef knives, .-thezlength; of travel; of the knit/'estres'- quired tooperatelthefjacks and theglength et.,

` theg knife-operating; arms; are;- correlated; tio!` cause; theknivesA Yto vthe-jacksA l:to i their?k midf positions. whenfjth lay operatingfcrank. shaft isattront centerl n 1 it;4 In aloom,adobbyfhavingfapair ofisllidt-f ing li ariiess l frame. j ack-operating@knyea, .as three-,armed .lever-.S ulcruined 'miclwa'y i theI planes of movement off the knives: toswing;4 in a :plane transversely' of :thevknifves,1.aorarlfk.r

is at front center and to canse the knives to'be oppositely disposed with the jacks at their end positions when the lay operating crank 95.

shaft is at back center.

5. A loom dobby having a pair of harness frame ack-operating knives sliding in planes symmetrically, oppositely and angularly disposed with respect to a Vcentral khorizontal path, a three-armed lever fulcrumedon an f aXis in the central plane to swing transversely of the knives, a crank having its axis ofV rof tation parallel to the said central plane,rajv

link connecting the crank and the centralv arm of the lever and links connecting the knives, in which the angular lrelationof the knife-operating arms to the center larm of` i Y connecting the crankto the center arm of the lever are Vcorrelated to cause the knives tov bring the jacks to their mid positions when the 'center arm of the lever is in the said central plane and when the crank is at either mid treme. jack-moving positions. V Y u 6.' A loomdobby having a Vpair ofharness frame jack operating knives sliding in planes f symmetrically, oppositely and angularly dis-V posed with respect to a central horizontal path, a three-armed lever fulcrumed on an axis in the central plane to swing transverse` ly of the knives, a vcrank having its'axis'of i rotation parallel to the said centralplane, Ya link connecting'the crank and the central arm of the lever and links connectingthe 195. other arms of the lever respectively to the Y" other arms of the lever respectively to the knives, in which the angular relation of the knife-operating arms to the center arm of the lever, the angular relation of the operating planes of the knives to the central plane, the length of travel of the knives required to operate the jacks, the length of the knife-operating arms, and the length of the link connecting the crank to the center arm of the lever are correlated to cause the knives to bring the 'jacks to their mid positions when the center arm of the lever is in the said central plane and when thercrank is Aat either mid point of its arc'of movement between its extreme jack-moving positions and to cause the knives to be oppositely disposed with the jacks at their end positions when the crank is at either of its eXtreme jack-moving positions.

In testimony whereof, I have signed my name to this specification.

VERNER LINDSJO. 

